The Northstar V-8 engine produced by General Motors initially for Cadillac is a reliable, technologically-advanced engine that has been in service since 1992. The Northstar, which GM considered its signature engine, suffered early problems. Oil leaks and blown head gaskets plagued early models, but other assorted flare-ups annoyed owners as well. Yet the Northstar evolved into one of the most respected engines to power a luxury vehicle.
The Northstar debuted on the ill-fated Cadillac Allanté, a two-seater roadster that Cadillac hoped would compete head to head with the sports car line-up coming from Germany and Japan. The Allanté was an epic failure, but the Northstar survived for nearly 20 years until GM announced it was retiring the venerable engine in 2010. Most Northstar versions displaced 4.6 litres and could generate up to 300 horsepower. A 4.4-litre version produced from 2006 to 2009 generated up to 469 horsepower in the Cadillac XLR-V and STS-V. A four-liter version powered some Oldsmobiles, according to Autotropolis.com and Allanteatlanta.com.
Precisely because the Northstar was a high-performance engine, in many ways it behaved like a delicate flower. It was an engine much like the high-performance Mercedes-Benz S-Class and Italian-made roadster motors. It could be temperamental with special needs. The Northstar featured a die-cast aluminium block. The bottom end girdle bisected the bottom of the engine along the centre of the crankshaft bearings. There were no main bearing caps found on other engines. However, the engine was prone to oil leaks because aluminium was porous. GM in 2000 developed a new process that “squeezed” the lower crankcase casting to reduce leaks.
Normal Is Relative
In the 1990s, the Northstar V-8 had four primary problems: head gasket failure, oil leaks, high oil usage and oil burning. Cadillac enthusiasts generally dismissed high oil use as a problem, noting that it’s not uncommon for high-performance engines to use a large amount of oil. GM noted that one quart of oil per 1,000 miles was not unusual since 32-valve tubes must be adequately lubricated. What’s not normal was the build-up of carbon in the rings that also led to high oil use. A GM-made cleaning kit usually solved the problem.
A Fine Mess
Common among the 1996 to 1999 Northstar V-8s were oil leaks originating at the rear main crank seal. Part of the problem was due to the aluminium block but also the seating of the oil seal in the block. GM solved the problem by developing a rear main oil seal that pressed into the block. It could only be removed and replaced by a special GM service tool.
Hot Button Issues
Head gasket problems also plagued the Northstar. Burning oil and the resulting build-up of debris in the engine caused it to overheat and blow a gasket. In other instances, the heads may have been serviced or replaced and then reinstalled with a new head gasket using the original head bolts. The threads of the original head bolts were weakened after removal and no longer secured the head and gasket properly. New head bolts were required. Replacing the head bolts out of sequence and at the wrong torque values could also lead to a blown head gasket.